Batteries are used extensively in notebook computers, cell phones, tools, transportation vehicles (e.g., electric cars, trains, buses, etc.), and other systems that depend upon an electrical source to function. Rechargeable batteries, such as lithium-ion batteries, may be the battery of choice due to their relative low cost and high energy storage capability.
A battery uses chemical energy (internal ion transfer) to perform electrical work (external electron transfer). A battery includes two external contact areas (anode and cathode) and an electrolyte. The anode is negatively charged relative to the cathode and, by connecting the anode and cathode to an electronic load, the battery provides power to the electronic load by passing electrons from the anode to the load and back to the cathode. The electrolyte is an ion conductor and an electron insulator. Meaning, the electrolyte passes ions between the anode and cathode, but suppresses electron flow between the anode and cathode. As the battery passes electrons to the electron load (discharges) through its external contacts, the electrolyte passes ions from the anode to the cathode internal to the battery.